1. Field of the Invention
The present invention relates to a method of manufacturing a surface acoustic wave device suitable for wireless apparatuses, such as cellular phones.
2. Description of the Related Art
A method of manufacturing a surface acoustic wave device according to the related art will be described with reference to the drawings. FIG. 5 is a cross-sectional view of a surface acoustic wave device that is manufactured by a method of manufacturing a surface acoustic wave device according to the related art. FIG. 6 is a diagram illustrating a first process of the method of manufacturing a surface acoustic wave device according to the related art. FIG. 7 is a diagram showing a second process of the method of manufacturing a surface acoustic wave device according to the related art.
Next, the configuration of the surface acoustic wave device according to the related art will be described with reference to FIGS. 5 to 7. A base substrate member 51 made of ceramic has a housing portion 51b composed of a concave portion having an opening portion 51a at the top thereof. A plurality of terminals 52 are disposed on the base substrate member 51. In this case, the plurality of terminals 52 extend from the housing portion 51b to the outer surface the base substrate member 51.
Further, a surface acoustic wave element 53 is constituted by an insulator 54 made of ceramic and a plurality of comb-shaped electrodes 55 that are provided on one surface (top surface) 54a of the insulator 54. The surface acoustic wave element 53 is housed in the housing portion 51b, and the other surface (bottom surface) 54b of the insulator 54 is attached to the base substrate member 51 via a thermosetting adhesive 56 that is provided on a bottom portion 51c of the housing portion 51b. 
Furthermore, the terminals 52 and the comb-shaped electrodes 55 are connected to each other in the housing portion 51b by bonding wires 57, and a lid 58 is attached to an upper end of the base substrate member 51 to close the opening portion 51a. In such a manner, the surface acoustic wave device according to the related art is formed.
Next, the method of manufacturing a surface acoustic wave device according to the related art will be described with reference to FIGS. 5 to 7. First, in the first process, as shown in FIG. 6, a conductive film 59 made of carbon is formed on the one surface 54a of the insulator 51, and the plurality of comb-shaped electrodes 55 are conducted by the conductive film 59. The other surface 54b of the surface acoustic wave element 53 is disposed on the thermosetting adhesive 56 that is provided on the bottom portion 51c. 
Next, in this state, heating is performed to cure the thermosetting adhesive 56, such that the insulator 54 is adhered to the bottom portion 51c by the adhesive 56. Subsequently, in the second process shown in FIG. 7, the conductive film 59 is removed by oxygen plasma.
Next, as shown in FIG. 5, the terminals 52 and the comb-shaped electrodes 55 are connected to each other by bonding the wires 57 and then the lid 58 closes the housing portion 51b. In such a manner, the surface acoustic wave device according to the related art is manufactured.
According to the method of manufacturing a surface acoustic wave device according to the related art, in the state in which the plurality of comb-shaped electrodes 55 are conducted by the conductive film 59, the thermosetting adhesive 56 is heated, such that the insulator 54 is adhered to the bottom portion 59. Accordingly, pyroelectric breakdown between the comb-shaped electrodes 55 does not occur. However, the method of manufacturing a surface acoustic wave device according to the related art requires the process of providing the conductive film 59 for conducting the plurality of comb-shaped electrodes 55 and the process of removing the conductive film 59 by oxygen plasma. Therefore, the productivity is degraded and the manufacturing cost is increased.
According to the method of manufacturing a surface acoustic wave device according to the related art, in the state in which the plurality of comb-shaped electrodes 55 are conducted by the conductive film 59, the thermosetting adhesive 56 is heated, such that the insulator 54 is adhered to the bottom portion 59. Accordingly, the pyroelectric breakdown between the comb-shaped electrodes 55 does not occur. However, the method of manufacturing a surface acoustic wave device according to the related art requires the process of providing the conductive film 59 for conducting the plurality of comb-shaped electrodes 55 and the process of removing the conductive film 59 by oxygen plasma. Therefore, the productivity is degraded and the manufacturing cost is increased.